Trimming and Feature Flags

[rossgrambo]

Feature flags are transformed by our adapter into keys looking like:

{[FeatureManagement:Alpha, False]}

The TrimKeyPrefix happens after this transformation. Meaning trimming any of the following would cause the feature flag to be unreadable (no longer in the expected "FeatureManagement" section):

.TrimKeyPrefix("f");
.TrimKeyPrefix("fe");
.TrimKeyPrefix("fea");
.TrimKeyPrefix("feat");
// etc

Trimming usually has some sort of divider which helps mitigate this- but I think trimming in it's current state and feature flags simply don't make sense to interact.

I propose we do not trim the key value if we know it is a feature flag. This is not a breaking change- as any trimming of a feature flag today would break it from being a feature flag. (You could trim a FF into acting like a normal KV by removing the full "FeatureManagement"- but I suspect little to no one has a dependency shaped like that)

@jimmyca15 @zhiyuanliang-ms @samsadsam

[samsadsam]

Agree with the proposal.

[zhenlan]

This will become less relevant after we have support for the new feature flags as server side resources, but if we still do anything for the classic feature flags, the provider should ignore all feature flags altogether unless UseFeatureFlag is called.